How Far Apart Should Hemp And Marijuana Plants Be?

With the legalization of marijuana in full swing across the United States, growers all over the country have had to come to terms with the issues surrounding growing marijuana alongside other crops. These concerns are particularly important to hemp growers, for whom marijuana is seemingly a logical companion to their primary crop.

For growers who wish to plant marijuana and hemp within the same space or immediate vicinity, one of the main concerns is the possibility of cross pollination between the two species. There is therefore a need to keep the plants separated by a suitable distance.

Because the two plant species are so closely related, growing them in such close proximity to each other presents unique problems for the grower. With two – or even more – entirely unrelated species, cross pollination is simply not an issue, even if the plants are laid out right next to each other. With hemp and marijuana however, the similarity in genetic makeup makes for a troublesome situation when both plant species are allowed to pollinate each other.

Beware of cross-contamination

In fact, the two species are so similar that allowing a male hemp plant to pollinate a female marijuana plant can be just as disastrous as allowing a male marijuana plant to pollinate a female marijuana plant. Male and female marijuana plants are of course typically kept apart from each other. This is to prevent pollination, which would result in the production of seeds instead of seedless flowers, which are far less desirable due to their taste and potency.

Many experts seem to agree that marijuana and hemp plants should be kept as far apart as possible. Anndrea Hermann, a noted authority in the hemp production industry, cited the risks involved in growing hemp and marijuana together. Hermann, who has been granted a DEA permit for importing and exporting hemp seed in the United States, categorically stated that hemp and marijuana “don’t belong in cultivation together”.

Pollen travels far in strong winds

Just how far apart should hemp and marijuana plants be placed? Drawing from information in a report released by the Oregon Cannabis Connection in 2015, Hermann said that pollen can travel anywhere from 5 to 12 kilometers. In fact, pollen has even been known to travel from Morocco to Spain across the Mediterranean–a distance of 48 kilometers.

Although few growers have sea winds to worry about in their growing areas, winds over dry terrain may present some challenges. Hermann therefore recommends keeping marijuana and hemp plants at least 10 miles apart. Hermann further qualified that although there is no guarantee that keeping hemp and marijuana plants that distance apart will prevent cross-pollination, it at least provides a reasonable starting point for growers.

But what of indoor grows? With their limited space, the best option growers have is to use a suitable filtration system installed by a qualified filtration specialist. Hermann recommends the use of HEPA or High Efficiency Particulate Air filters, which are effective at filtering out pollen. Hermann further recommends periodic maintenance of the filter system, and communication between all hemp and marijuana growers in the vicinity.

Based in California, Ben writes about marijuana culture, cultivation and edibles. He's a regular contributor at marijuanamarketplace.com, themarijuanachef.com, marijuanagrowhelp.com, and stonerthings.com